With the help of NASA’s Spitzer Space Telescope, a team of astronomers affiliated with the National Optical Astronomy Observatory (NOAO) in Tucson, Arizona, think they might have spotted the first examples of extragalactic carbon-based molecules in space: fullerenes and graphene.
And they also think they have an explanation for why those molecules are there: shocks from collisions between bits of carbon blown about by the strong stellar winds found in planetary nebulae. Their conclusions appeared in a recent paper published in the Astrophysical Journal Letters.
Fullerenes, more commonly known as “buckyballs” because of their unique shape, calling to mind the geodesic domes that were the trademark of architect Buckminster Fuller. C60 looks like a soccer ball, while C70 resembles a rugby ball. Their unique structure gives them many useful properties for potential application, most notably future electronics, and for many years, fullerenes were all the rage until that upstart, graphene, came along.
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There was some doubt as to whether this form of carbon was even possible — for it to be truly 2D it would have to be a mere atom thick, making it also highly unstable — but Andre Geim and cohorts at the University of Manchester in the UK succeeded in creating sheets of graphene in 2004, in perhaps the most ingenious use of scotch tape yet devised.
Geim and Konstantin Novoselov shared the 2010 Nobel Prize in Physics for their graphene research.
Much has been made of the graphene’s potential for creating ultrafast molecular-scale transistors, especially the fact that the electrons in graphene zip along at the speed of light, as if they had no mass — contrary to special relativity, which says no object with even the tiniest bit of mass can exactly reach the speed of light.
Other results suggest that graphene can also shoot electrons through other materials as if they were invisible, similar to quantum tunneling, in which electrons can tunnel through supposedly insurmountable energy barriers. It’s the kind of bizarre behavior that would normally require superheavy atoms or black holes. Some physicists have even suggested that graphene provides a useful analog model for understanding the Higgs boson.
So apart from all its potential practical applications, graphene provides an interesting tabletop medium to probe some of these unusual phenomena. And now it looks like graphene and its carbon cousins, the fullerenes, could also shed light on stellar evolution — particularly how complex organic molecules form and evolve within stars — as well as the physical processes involved with the biochemistry of life.
The planetary nebulae — star systems with shells of surrounding gas that resemble the disks surrounding Jupiter and Saturn (hence the name) — that are playing host to these exotic molecules are in the Large and Small Magellanic Clouds next to our own Milky Way galaxy.
They mostly look like fuzzy blobs because they’re so far away, but astronomers have been able to determine the distance pretty accurately (within 5 percent). That’s important because it also enables them to determine the luminosity of the stars within them and verify that, yes, those fuzzy blobs really are planetary nebulae.
The various instruments aboard Spitzer Space Telescope have proved valuable for things like spectroscopy, used to study the kinds of complex organic molecules that tend to thrive in these kinds of environments, and carbon-based molecules are particularly prevalent, unlike, say, metals. (Hydrogen and helium are everywhere, natch.)
It can be tricky to detect the telltale spectral signatures of fullerenes and graphene in distant space, but this is strong evidence that fullerenes and graphene might be quite abundant in our universe. And it’s an exciting first step towards a more complete understanding of how these and other complex organic molecules form and evolve inside stars.
Technically, the discovery still needs to be confirmed with laboratory spectroscopy, although team leader Domingo Anibal Garcia-Hernandiz of Spain’s Instituto de Astrofisica de Canarias has noted that this is “almost impossible with the present techniques.” But plans are underway for a follow-up analysis using NOAO’s various ground-based telescopes.
Top image: Artist’s conception of fullerene and graphene molecules superimposed over the Helix Nebula (IAC). Bottom: The Large Magellanic Cloud planetary nebula known as SMP48 (STSci and MCPN Project Team).